Railway track circuit apparatus



Jan. 5, 1943.

G. w. BAUGHMAN RAILWAY TRACK CIRCUIT APPARATUS Filed July 27, 1940 Mb n T 9 m J T\! mi 1 m W 3 6 S a a Wm M Q a 5 mam C 5E TH M MN J NU WK 1 .Q u m a am 3 N an x M Q 4 MN m w M WE $1 m R w w v3 Q bi N. LN RE C1... vs 7 MU am mm Wm Mm NM n w JUN NA UN\ \N m 1 J u S Q Q R Q,

Patented Jan. 5, 1943 UNi'i'ED STATES r e r orrlcs RAILVJAY TRACK CIRCUIT APPARATUS George W. Baughman,

to The Union Switch Pittsburgh, Pa., assignor & Signal Company, Swiss- 7 Claims.

My invention relates to railway track circuit apparatus; and it has particular reference to the organization of such apparatus into novel and improved forms of railway track circuits.

In order to enable a train on a track to establish control over traffic controlling or signaling devices at definite points along the track, it has been customary heretofore to utilize at least one and usually two insulated joints at each diiferent control point on the track. In systems where two insulated joints are employed at control points, it has been the practice to provide separate and individual track circuits for the length of track defined by each two successive pairs of insulated joints. A system of this class is relatively expensive to install and maintain when the sections are short, since each control section requires not only that both track rails be divided by insulated joints but also each section requires a track relay and a track circuit current source.

In systems where but one insulated joint is employed at a control point intermediate the ends of a track section, it has been proposed either to provide each joint with a track relay connected around the joint so as to be shunted as the train advances past the insulated joint, or to provide each joint with an impedance which when shunted out by a train abruptly changes the current flow in a relay connected in circuit with the track rails at the exit end of the circuit, whereby the relay may be caused to pick up or release, in accordance with the connection of the relay in the circuit, in response to the abrupt change of current flow in the circuit. A system of this latter class also is relatively expensive to install and maintain when several different control points are required because it requires the provision of insulated joints in oneof the track rails, and if such a system is provided on a stretch of electrified trackway where the track rails are employed as return conductors for electrical propulsion current, an impedance bond must of course be provided for each insulated joint.

It is an object of my present invention to provide definite points of control in a track section independently of the provision of insulated joints at such points.

Another object is the provision of novel and improved railway track circuits incorporating means for obtaining additional points of controlin a section without requiring the section to be subdivided by cut sections. 7,

A further object of my invention is the provisionof novel and improved railway track circuits incorporating means arranged to provide additional points of control in a section independently of the provision of additional insulated joints at such points, and wherein the points ofv jects and characteristic features of my invention which will become readily apparent from the following description are attained in accordance With my invention by incorporating intoa track circuit supplied with current from the secondary winding of a transformer having its primary winding connected to a source of alternating A current, means energized from the source and responsive to a change in phase angle between currents in the secondary winding of thetransformer and in said source, caused by a train in the section shunting the track rails. Such means may comprise a two-element alternating current track relay having one element connected to be energized by current supplied from the secondary winding of the track transformer and having its other element connected to the alternating cur- Q rent source.

The phase angle or displacement between the currents in the two elements of the track relay is adjusted to a normal value when the section is unoccupied, and the normal value of this angle is so selected that as a train advances through the section to shunt the track rails and continually decrease the length of rail between the train shunt and the exit end of the section, and hence decrease the impedance connected in circuit with the track element of the relay,the phase angle between the currents continually changes and the relay is caused tooperate when the train reaches a point in the section such that the impedance of the track rails reaches a predetermined value. Additional means may be provided for altering the phase angle after operation of the relay to cause the relay again to assume its initial position until further operation of the train and further change in the efiective impedance of the track rails causes a further change in the phase angle and another operation of the track relay.

I shall describe a few forms of railway track circuit apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view illustrating a preferred form of railway track circuit apparatus embodying my invention. Fig. 2 is a diagrammatic view illustrating a modified form of the apparatus shown in Fig. 1, and also embodying my invention.

Similar reference characters have been employed to designate corresponding parts in each of the two views.

Referring to Fig. 1, the reference characters I and la designate the track rails of a stretch of railway track over which traffic normally moves in the direction indicated by an arrow, and which rails are divided by means of the usual insulated joints 2 into track sections DF and F--J. Each section is provided with a novel and improved form of track circuit embodying my invention, and each track circuit includes an alternating current track relay, designated by the reference character TR with a distinguishing suiiix, connected across the rails of the section adjacent the entrance end, and the secondary winding 6 of a track transformer, designated by the reference character T1 with a distinguishing sufiix, connected in series with the track element of a two-element alternating current track relay, designated by the reference character R with a distinguishing suffix, across the rails of the section adjacent the exit end. The primary winding 1 of each track transformer T1 is connected through a current limiting impedance or resistor 8 to a suitable source of alternating current, such as a generator not shown but having its opposite terminals designated in the drawing by the reference characters BX and GK; and similarly the other or local element 9 of each track relay R is connected through a current limiting impedance or resistor Hi to the source of alternating current. Track relays TR may, of course, be of the two-elementtype, but as this is not essential to my invention, such relays are represented in the drawing for simplicity as being single-element alternating current relays.

The track circuit of section FJ additionally has associated therewith an auxiliary relay SR having a pick-up circuit which may be traced from one terminal B of a suitable source of current, such as a battery not shown, through back contact [2 of track relay TRF, back contact 53 of track relay RJ, and the winding of relay SR to the other terminal C of the source of current; and also having a stick circuit which corresponds to its previously traced pick-up circuit except that front contact 14 of relay SR replaces back contact l3 of relay RJ. Relay SR when released closes back contact It to shunt a condenser I6 connected in series with impedance l9 and local winding 9 of relay RJ.

The parts of the apparatus comprising the track circuits illustrated in Fig. 1 are constructed and arranged in such manner that when a section is unoccupied, the associated track relay TR is energized and picked up by the current supplied to the rails of the section from secondary winding 6 of the associated track transformer T1. In addition, the currents in the track element and in the local element 9 of each two-element track relay R is adjusted by suitable means, as by impedance H1, so as to produce a phase angle or displacement of predetermined value between such currents. As shown in Fig, 1, the parts are proportioned and adjusted in such manner as to produce a phase difference between the currents of the order of 30, and as a result the two-element track relays R are picked up. It is, however, to be understood that if it is desired to employ the relays R as normally released relays, the normal phase angle could then be adjusted to a smaller value such that the relays normally are deenergized.

With the track circuit apparatus in its normal condition as shown in Fig. 1, the entrance of a train on section DF shunts relay TRD to release that relay. As the train proceeds through the section, it shunts out more and more of the reactance of the track rails connected in circuit with transformer secondary winding 6 and the track element of relay RF, so that as a result the track current, which is fed through a limiting resistor, moves in a direction to be more nearly in phase with the voltage at the source. In the particular arrangement of apparatus shown in Fig. 1, this change causes the phase displacement to decrease, and by properly proportioning the apparatus, relay RF can be made to release when the train reaches a predetermined point such as E in the section and shunts out a predetermined length of track rail from the track circuit. Conversely, if the relays R are adjusted normally to be released, the apparatus of Fig. 1 can be adjusted to widen the phase displacement between the currents in the two elements of relay RF as the train proceeds through section D-F, with the result that when the train reaches a predetermined point E in the section and shunts out a predetermined amount of track rail impedance, the phase displacement can be adjusted to reach the value at which relay RF is caused to pick up.

Inasmuch as the phase displacement of the currents in the two elements of relay RF is a function of both the track rail impedance and the track ballast leakage resistance, and since these control factors are in multiple, it is evident that if the apparatus is adjusted to cause relay RF to release at a point in the section where the effect of the track ballast resistance is negligible, this point will be substantially independent of ballast resistance variations. I have found that if two-element relay RF-connected as shown in Fig. 1 is adjusted to release when a train is 1,500 feet or less from the relay with cycle current supplied to the rails or 1,850 feet with 60 cycle current supplied to the rails, the effect of ballast resistance variations is practically negligible and as a result the point at which the relay releases is substantially independent of ballast resistance conditions.

After relay RF releases, both relays TRD and RF remain released until the train vacates section DF, whereupon both relays become reenergized and the track circuit apparatus of section DF is restored to its normal condition.

When the train enters section F-J, relay TRF is shunted and caused to release to' close its back contact 12 and thereby prepare the previously traced pick-up circuit of relay SR. The apparatus of section F-J is proportioned and adjusted so that when the train reaches a predetermined point, such as G, in the section and shunts out a predetermined length of track rail to reduce the effective impedance connected in circuit with secondary winding't of transformer TI-J and the track element of relay RJ, the phase displacement between the currents in the two elements of relay RJ assumes a value such that the relay is caused to release and to close its back contact 13. Relay SR thereupon picks up to close its front contact I4 and thereby complete its previously traced stick circuit, and to open its back contact and thereby open the shunt circuit around condenser IE to render the condenser effective to advance the current in local winding 9 of relay RJ and cause the phase angle between the currents in the two elements of relay RJ to assume a value such that relay RJ picks up. Relay RJ remains picked up until the train reaches another predetermined point, such as H, in section FJ, where the length of track rail shunted by the train reduces the effective impedance connected in circuit with the track element of relay RJ to a value such that the phase displacement between the currents in the two elements of relay RJ again assumes a value too low to retain the relay picked up. Relay RJ thereupon releases and remains released until the train vacates section F-J, whereupon both relays TRF and RJ pick up and relay SR releases to restore the track circuit apparatus of the section to its normal condition.

In Fig. 2, a three-position, two-element alternating current relay RM is represented as having a local element 9 connected through impedance ID to a source of alternating current, and the track element of the relay is connected to the rails of section KM at its exit end through a secondary winding 6 of a transformer TTZ having its primary winding 1 connected through impedance 8 to the source of alternating current. The track element of relay RM is also supplied with current from another transformer T1! which has its primary winding 7 connected to the source of alternating current and has its secondary winding 6 connected through impedance Hi to the rails at entrance end K of the section. The currents in windings 6 of transformers TTI and 'ITZ are adjusted, as by impedances 8 and E8, to have a phase displacement of, say, 120 when the section is unoccupied, and the resultant of these currents in the track element of relay RM leads the current in local element 9 of the relay by an angle of the order of 30", thereby producing an efiective torque having a direction such as to cause contact member of the relay to operate to its normal or left-hand position, as represented in Fig. 2. When a train enters section KM and shunts the current of transformer TTI away from relay RM, the current in the track element of relay RM supplied from transformer TTZ then lags the current in the local element 9 by an angle of the order of 30, thereby producing an efiective torque of the opposite direction so as to cause the relay to operate its contact member 20 to its reverse or right-hand position, as viewed in Fig. 2.

The parts of the apparatus further are proportioned and adjusted in such manner that as the train proceeds through the section and shunts out more and more of the impedance of the track rails, the current in winding 6 of transformer TTZ moves in a direction to be more nearly in phase with the voltage at the source, with the result that when the train reaches a predetermined point, such as L, in the track circuit to shunt out a predetermined amount of track rail impedance, relay RM is caused to be released.

A relay RPM controlled over an obvious circuit governed by relay RM may be employed to detect whether relay RM is picked up in one position or the other, or is released. Relay RPM, of course, releases when; relay RM is caused torelease by the train reaching the point L in the track circuit, and relay RPM remains released until the train vacates the section and both track transformers TTI and TTZ become effective to supply current to the track element of relay RM to cause that relay to operate its contact member 28 to its normal position as shown.

Many places where track circuit apparatus embodying my invention may be used will readily suggest themselves to those trained in the art, but a particularly effective use of such apparatus may be made in systems wherein the speed of a train approaching a highway crossing is measured and operation of the crossing signal is initiated in accordance with the measured speed of the train. One such system of this class is shown in United States Letters Patent No. 2,113,641, granted to me on April 12, 1938, for Railway signaling apparatus, wherein a timing device is reset and a new operation of the device is effected whenever a train requires more than a predetermined time interval to pass between successive control points along the track. By use of the track circuit apparatus shown provided for sec tion DF in Fig. 1 or section KM in Fig. 2, it is apparent that a train mayv effect in a single insulated section of track three distinct controls, a first when the train enters the section, another control when the train reaches the predetermined point in the section, and the third when the train vacates the section. Correspondingly, it is evident that when the track circuit apparatus shown provided for section F'J of Fig. l is employed, a train in the single insulated section of track may efiect four distinctive controls, a first when the section is entered; a second due to the release of relay RJ when the train reaches the first predetermined point G in the section; a third control when the relay again releases due to the train arriving at the second predetermined point H in the section (the first release of relay RJ causing relay SR to pick up to condition relay RJ to be reenergized and picked up so that the third control may be established) and the fourth control whenthe section is vacated.

It is apparent from the foregoing that apparatus embodying my invention provides novel and improved track circuits so arranged as to enable an increased number of controls to be established by a train in a single insulated section of track. It follows, therefore, that my invention provides means whereby additional controls may be effected by a train on a track without requiring the section to be subdivided by cut sections using insulated joints, thereby greatly reducing the initial and maintenance costs of obtaining such additionalcontrols.

Although I have herein shown and described only a few forms of track circuit apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

iHavin'g thus described my invention, what I claim is:

1. In combination, a section of railway track, a two-element alternating current relay having one of itselements connected-to a source of alternating current, a transformer having its primary windingconnected to said source and its secondary winding connected through the other element of said relay to-the rails of said section, means for adjustingthe phase angle between currents in the two elements of said relay to a normal value efiective to cause said relay to be picked up when said section is unoccupied and to be released when a predetermined length of track rail is shunted by a train in the section, and other means-controlled by said relay for readjusting said phase angle after said relay releases to cause said relay to pick up.

2. In combination, a section of railway track, a two-element alternating current relay having one of its elements connected to a source of alternating current, a transformer having its primary winding connected to said source and its secondary winding connected through the other element of said relay to the rails of said section, means for adjusting the phase angle between currents in the two elements of said relay to a normal value effective to cause said relay to be a picked up when said section is unoccupied and to be released when a first predetermined length of track rail is shunted by a train in the section, and other means controlled by said relay for readjusting said phase angle after said relay releases to cause said relay to pick up and remain up until the-train shunts another predetermined length of rail of said section.

3. A railway track circuit comprising, in combination, a section of railway track having a track relay connected to the rails at one end of the section, a two-element alternating current relay having one of its elements connected to a source of alternating current, a transformer having its primary winding connected to said source and its secondary winding connected through the other element of said two-element relay to the rails at the ther end of said section, means for adjusting the phase angle between currents in the two elements of the said two-element relay to a normal value effective to cause said two-element relay to be picked up when said section is unoccupied and to be released when a first predetermined length of track rail is shunted by a train in the section, and means controlled by said track relay and said two-element relay for readjusting said phase angle after said twoelement relay releases to cause said two-element relay to pick up and remain up until the train shunts another predetermined length of rail of said section.

4. A railway track circuit comprising, in combination, a section of railway track having a track relay connected to the rails at one end of the section, a two-element alternating current relay having one of its elements connected to a source of alternating current, a transformer having its primary winding connected to said source and its secondary winding connected through the other element of said two-element relay to the rails at the other end of said section, means for adjusting the phase angle between currents in the two elements of said two-element relay to a normal value efiective to cause said two-element relay to be picked up when said section is unoccupied and to be released when a first predetermined length of track rail is shunted by a train in the section, a stick relay provided with a pick-up circuit including a back contact of said track relay and a back contact of said twoelement relay and having a stick circuit completed over its own front contact and a back contact of said. track relay, and means controlled by said stick relay for readjusting said phase predetermined length angle to cause said two-element relay to pick up and remain up until a second predetermined length of rail is shunted by the train in the section.

5. Railway track circuit apparatus for use with a source of alternating current and a section of railway track having an impedance connected across its track rails atone end of said section, said apparatus comprising a two-element alternating current relay having one of its elements connected to said source, a transformer having its primary winding connected to said source and having its secondary winding connected across said track rails at the opposite end of said section in series with the other of said two elements for supplying thereto current which has a predetermined phase relationship with respect to the current in said one element to operate said relay to an initial position when said section is unoccupied and to retain the relay in such position after said section becomes occupied by a train which enters at said one section end until the train advances to a preselected point intermediate the two section ends to shunt. out a of track rail, thereby to vary the said predetermined phase relationship and cause said relay to operate to another position.

6'. A railway track circuit of the alternating current class wherein an alternating current track relay coupled across the track rails at one end of a section is energized by current supplied from a source of alternating current coupled across said rails at the opposite end of said section, characterized by the provision in such circuit of control means comprising a two-element alternating current relay having one of said two elements interposed in series in the coupling of said source across said track rails and having the other of said two elements supplied with energy from said source, said two elements being adjusted to have a predetermined phase relationship of currents therein effective to cause said two-position relay tooperate to a normal position when said section is unoccupied and to remain in said normal position after said section becomes occupied by a train until such train advances to a preselected point in said section intermediate its ends to shunt out a predetermined length of track rail, thereby to vary said predetermined phase relationship and cause said two-position relay to operate to another position.

7. In arailway track circuit of the alternating current class wherein an alternating current relay coupled across the rails of a section of track receives energy from a source of alternating current coupled across said rails at the opposite end of said section, the combination of a two-element alternating current relay having one of its said two elements interposed in series in the coupling of said source across said rails and having the other of said two elements supplied with energy from said source, said two-element relay being adjusted to have a predetermined phase relationship of currents in said two elements,

whereby to cause said two-element relay to assume an initial position until a train in said section advances to a point intermediate the ends of said section and shunts out a predetermined length of track rail, thereby to vary said predetermined phase relationship and cause said twoelement relay to assume another position.

GEORGE W. BAUGHMAN. 

